Generally, as a method for producing products in aluminum or magnesium industries, there are various methods such as a casting method for making a desired shape by melting metal and a method for mixing and sintering powder type raw materials. A high temperature melting casting technology is most frequently used in the method. However, one of the main factors of determining a quality of products in the aluminum or magnesium casting process is an amount of dissolved hydrogen which is generated by penetrating moisture decomposed in the atmosphere into molten metal. Since the dissolved hydrogen has a difference in solubility of about 10 to 20 times in a liquid state and a solid state, the hydrogen is agglomerated at the time of coagulation of a molten aluminum-magnesium alloy and thus pores are formed. These pores not only degrade strength of products but also damage appearance, which is emerging as an important issue in the aluminum or magnesium industries. To solve the problem, a degassing process of forcibly extracting the hydrogen within the molten metal using argon or chloride gas has been carried out in the industrial site. However, the degassing process has a considerable difficulty in making products having a constant content of hydrogen since time required for the degassing process is changed due to the surrounding environment in which the molten metal is melted, a content of impurities within the molten metal, and weather effects of humidity, temperature, or the like. Therefore, a need exists for a development of a hydrogen sensor which may control a quality of molten metal with a constant content of hydrogen by monitoring the content of hydrogen within the molten metal in real time, independent of the surrounding factors.
However, a technology which is mainly used to measure the content of hydrogen within the molten metal in producing the aluminum or magnesium products uses a method for cutting the product coming out after coagulating the molten metal and observing pores within the product to calculate the content of hydrogen; however, for the measurement of the content of hydrogen based on the method, may not avoid a breakage of a final product.
Further, another method uses a hydrogen sensor which measures the content of hydrogen within the aluminum or magnesium molten metal and uses only a hydrogen ion solid electrolyte and therefore blows gas having a standard hydrogen concentration into one surface of an electrode (reference electrode) to fix a hydrogen concentration of the reference electrode and putting the other surface of the electrode into the molten metal to measure an electromotive force generated due to a difference between a hydrogen partial pressure within the molten metal and a hydrogen pressure of the standard gas, thereby measuring the content of hydrogen within the molten metal. However, due to the standard hydrogen gas of the reference electrode used to fix the hydrogen partial pressure, a gas barrel is accompanied at all time at the time of the measurement and therefore the measurement apparatus becomes huge and a gas demand is continuously generated, such that the inconvenience of measurement and the problem of costs and safety due to transportation and frequent replacement of the reference hydrogen gas barrel occur.
Further, to solve the problem, as illustrated in FIG. 1, there is a hydrogen sensor for aluminum (alloy) molten metal (Korean Patent No. 10-0499044) configured to include a hydrogen ion conductor 1, a solid reference material 4 filled in the hydrogen ion conductor 1, a ceramic cover 5 formed on the solid reference material, a reference electrode 2 formed between the solid reference material 4 and the hydrogen ion conductor 1, a measurement electrode 3 formed outside the hydrogen ion conductor 1, and a wire 6 connecting the reference electrode 2 to the measurement electrode 3. The hydrogen sensor for aluminum molten metal may be configured to measure the concentration of hydrogen by fixing the hydrogen partial pressure of hydrogen which becomes a reference using Ti/TiH2/TiO, Ca/CaH2/CaO, or the like which is the solid reference material 4 but requires a high temperature sealing technology of sealing gas at a high temperature and therefore may cause a problem of making a structure of packaging complex.